1. Field of the Invention
This invention relates to an apparatus for transferring solid materials between zones of substantially different pressures, the solid materials being supplied to a lockhopper containing a liquid having a density less than the solid materials, the solid materials with associated liquid passing through a solids-liquid separator chamber separating the solid materials and liquids so that the solid materials substantially free of liquids, are passed into a vessel such as a pressurized reaction vessel. The liquid in the lockhopper acts as a liquid seal between the pressurized reaction vessel and lockhopper which is at a much lower pressure. Utilization of the solids-liquid separator chamber provides more rapid recycling of the lockhopper, prevents liquid from being carried into the reactor vessel if there is a pressure surge and allows handling finer solid materials.
2. Description of the Prior Art
Several methods utilizing different apparatus have been used in the past for the introduction of solids into pressurized reactors. Gas pressurized lockhoppers have been used for transferring solids into a pressurized reactor. Solids are added to a lockhopper at ambient pressure and the lockhopper closed and pressurized with gas to the pressure of the reactor. The solids are then added to the reactor which is at about the same pressure as the lockhopper. The lockhopper must then be isolated from the reactor and reduced to ambient pressures for introduction of the solid materials. Gas pressurized lockhoppers require complicated valving and in practice, have long cycle times.
Lockhoppers are frequently constructed in the form of a long gravity feed leg above the reactor to overcome the pressure differential and thus are feasible over relatively small pressure differentials in the order of about 10 psi, due to the high pressure legs required. U.S. Pat. Nos. 2,626,230 and 2,885,099 relate to different gravity feed leg configurations but do not overcome the basic problems of length of the leg required for high pressure differentials.
High density liquids are suggested by U.S. Pat. Nos. 2,704,704 and 3,009,588 to develop the desired pressure differential, but the liquids suggested, such as molten lead, mercury, tin, provide severe economic and environmental disadvantages.
Sealing liquid such as water, is suggested by U.S. Pat. No. 2,828,026 in a system employing a drum with rotating feeder buckets. The operating pressure of a retort is balanced by a liquid standpipe and is again restricted to use over small pressure differentials, due to the height requirements of the liquid standpipe.
U.S. Pat. No. 2,925,928 suggests feeding coarse solids through a fluidized bed of finely divided solids in a standpipe to balance the pressure difference between two zones of different pressure. However, use of this system over pressure differentials of only about 10 to 20 psi is practical.
U.S. Pat. No. 3,729,105 teaches a lockhopper which contains liquid, serving as a liquid seal, through which a higher density solid falls and is fed to a pressurized vessel by a feeder, such as a screw feeder. This system may be used with higher pressure differentials than prior systems, but has disadvantages of the solids carrying undesired liquids into the pressurized vessel, especially with small particle size solids, and permits the liquid to be carried into the pressurized vessel, such as a reactor, if there is a depressurization surge in the reactor. It is apparent that in many reaction systems entry of the liquid into the reactor may be ruinous.